Field of the Invention
The present invention relates to an inductor-less LNA (Low Noise Amplifier) with a blocking function which is used in a communication system.
Background of the Invention
This section is just to provide background information related to embodiments of the present invention but is not intended to explain conventional techniques related thereto.
As is known in the related art, ISDB-T (Integrated Service Digital Broadcasting Terrestrial) uses a UHF (Ultra High Frequency) frequency band (470 MHz to 707 MHz), ISDB-Tmm (Integrated Service Digital Broadcasting Terrestrial Mobile Multi-Media) uses a VHF (Very High Frequency) frequency band (170 MHz to 280 MHz), and ISDB-Tsb (Integrated Service Digital Broadcasting Terrestrial Sound Broadcasting) uses an LVHF (Low Very High Frequency) frequency band (90 MHz to 110 MHz). Among these, the ISDB-Tmm scheme has been devised for mobile broadcasting based on the ISDB-T scheme which is being currently used for terrestrial digital TV broadcasting. That is, the ISDB-Tmm scheme can offer a fused service for two media, i.e., communication and broadcasting having different properties.
In mobile tuner environments supporting the above-mentioned ISDB-T, ISDB-Tmm and ISDB-Tsb, a TV receiving chip and an antenna are relatively distant from each other. This may produce a line loss, which may result in increase in NF (Noise Figure) and hence deterioration of reception sensitivity.
In order to minimize such deterioration of reception sensitivity, there has been conventionally proposed a method for additionally using a small capacity low noise amplifier disposed immediately before the antenna to increase the reception sensitivity of the TV receiving chip against the line loss. However, recent use of an LTE (Long Term Evolution) band ranging from 700 MHz to 2.4 GHz for mobile phones deteriorates the performance of the ISDB-T of the UHF frequency band (470 MHz to 707 MHz). The reason for the performance deterioration will be described below with reference to FIG. 1.
FIG. 1 shows a channel environment of a conventional LNA.
Referring to FIG. 1, in a channel environment for a mobile TV tuner, a desired channel has less power, whereas ambient channels have more power. Therefore, in order to avoid such power unbalance, there is a need to increase the linearity of the LNA such that harmonic tones of the ambient channels have no effect on the desired channel.
If the LNA supports ISDB-Tmm, in general, two amplifiers are used to support a frequency band. An LNA may be used to support a UHF frequency band and a VHF frequency band in a wide range. However, in mobile environments, if a large input signal with jammer power occurs in a frequency band adjacent to the desired channel, an interference may occurs between signals of the desired channel. Therefore, there is need to reduce an interference between adjacent frequency bands. In addition, there is a need to reduce an interference between frequencies of FM signals used between a UHF frequency band and a VHF frequency band and an interference between UHF adjacent frequency bands such as CDMA (Code Division Multiple Access), LTE (Long Term Evolution) and the like.